JPH0575603U - Cylinder with position detector - Google Patents

Abstract

(57) [Abstract] [Purpose] The error caused by the displacement of the rotary encoder when the piston moves forward and backward can be corrected without returning to the origin position, and the position where the reset or offset position does not change due to temperature change. It is a cylinder with a position detector provided with a detector. An offset detection element for detecting a piston is provided in the middle of a cylinder, and each time the piston reaches the position of the offset detection element, the counter value is corrected to the number of offset pulses. Also, as the offset position detection circuit, a detection signal is output at the peak of the output of the offset detection element, and the value of the counter is corrected to the number of offset pulses based on the detection signal output of this offset position detection circuit.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a cylinder in which a stroke of a piston that moves forward and backward by hydraulic pressure or air pressure is pulsed by an encoder, and the pulse is counted to detect the stroke of the piston.

[0002]

[Prior Art]

 Conventionally, in a cylinder with a position detector, as shown in FIG. 8, a piston (2) connected to a rod (4) is inserted into the cylinder (1) so that the piston (2) can move back and forth, and the rod (4) of the cylinder (1) is ) Was provided with a rotary encoder (8). Further, the piston (2) has a built-in magnet (3), and the origin magnetic detection element (7) is provided on the outer surface of the cylinder (1) at a position corresponding to the origin of the piston (2). It was received.

The rotary encoder (8) is provided with a roller (9) that rolls in contact with the surface of the rod (4). In this rotary encoder (8), the roller (9) is impossible. The roller (9) was mounted via a spring (10) so as to be pressed against the rod (4) at an appropriate pressure so as to roll without any action.

The output of the origin magnetic detection element (7) has a characteristic as shown in FIG. 7 (a), and this waveform is pulsed with a threshold S as shown in FIG. 7 (b). At the rise of this pulse, the count of the pulse from the rotary encoder (8) is reset.

[0005]

[Problems to be solved by the device]

 As described above, the cylinder with position detector is mounted so that the rotary encoder (8) presses the roller (9) to the rod (4) via the spring (10). It has a slight degree of freedom in the front, back, left and right so as not to hinder the pressure. When the piston (2) is moved back and forth in such a mounted state of the rotary encoder (8), the rotary encoder (8) is pulled in the moving direction of the piston (2) and moves by the degree of freedom.

The degree of freedom of the rotary encoder (8) is almost a problem because the degree of freedom in the traveling direction is lost when the piston (2) once stops and then moves in the same direction. However, if it stops for a while and then moves in the opposite direction, the rotary encoder (8) is pulled and moved by this degree of freedom, and the roller (9) does not roll. During this time, the rotary encoder (8) However, there was a problem that no pulse was output.

To briefly explain a concrete example, when the degree of freedom is 0.2 mm, it advances from a certain position by 50 mm based on the output of the rotary encoder (8) and stops at a point A. If it is advanced further 50 mm and stopped again at point B, and if it is attempted to retreat from this point by 50 mm and stop at point A, the stop position will not be the exact point A but will be a position retracted 0.2 mm further from point A.

[0008] Actually, the error caused by the mounting state of the rotary encoder (8) and the change from forward to backward or from backward to forward differs depending on the mounting condition of the piston (2). There was a problem that the difference between the above-mentioned errors was accumulated during repeated forward / backward movements, resulting in a large accumulated error. In order to prevent this accumulated error, the piston (2) moved forward once or several times. There was a problem that the piston (2) must be returned to the home position and reset after the backward movement.

Further, the magnetic sensing element (7) has an output characteristic shown in FIG. 7 (a), and this characteristic has its output decreasing as the temperature rises, as shown by the broken line, and the broken line in FIG. 7 (b). As shown in, the pulse width becomes narrow, and it is difficult to always detect the same position as the origin. In particular, at the time of initial operation of the device, the temperature of the cylinder (1) rises and is not stable due to the temperature rise and pressure of the differential oil due to the temperature rise of the hydraulic pump.

The present invention can correct the error caused by the displacement of the encoder when the piston moves forward and backward without returning to the origin position, and the position where the reset or offset does not change due to temperature change. An object is to obtain a cylinder with a position detector equipped with a detector.

[0011]

[Means for Solving the Problems]

 The present invention has been made to solve the above problems, and an offset detecting element for detecting the piston is provided in the middle of the cylinder, and a counter is provided each time the piston reaches the position of the offset detecting element. The value of is corrected to the number of offset pulses. Also, the offset position detection circuit outputs a detection signal at the peak of the output of the offset detection element, and the counter value is corrected to the number of offset pulses based on the detection signal output of this offset position detection circuit. It was done.

[0012]

[Action]

 The offset detection circuit generates an offset position detection signal that does not change due to temperature changes, and the counter value is always corrected to the correct offset pulse number at the position of the offset detection element.

[0013]

【Example】

 Next, an embodiment of the hydraulic cylinder with a position detector according to the present invention will be described with reference to FIGS. 1 to 8. FIG. 1 is a sub-sectional view of a hydraulic cylinder with a position detector according to the present invention, in which a piston (2) connected to a rod (4) is inserted into the cylinder (1) so as to be able to move back and forth. ) Is provided with a first inlet (5) and a second inlet (6) for differential oil which are connected to a hydraulic pump (not shown) via solenoid valves.

A rotary encoder (8) is provided on the protruding side of the rod (4) of the cylinder (1). A magnet (3) is built in the piston (2), and a magnetic detection element (7) for origin is provided on the outer surface of the cylinder (1) at a position corresponding to the origin of the piston (2). Has been. Further, on the outer side surface of the cylinder (1), an offset magnetic detection element (11) capable of moving to an arbitrary position is provided.

The rotary encoder (8) is provided with a roller (9) that rolls in contact with the surface of the rod (4). The roller (9) rolls so that the roller (9) rolls comfortably. The spring (10) is attached to the rod (4) so as to press the rod (9) against the rod (4) so that it can be moved up and down to some extent.

As shown in FIG. 2, the output of the rotary encoder (8) is connected to the counter (13), and the output of the counter (13) is connected to the CPU (12). The offset magnetic detection element (11) is connected to the CPU (12) through the offset position detection circuit (14), and the origin magnetic detection element (7) is connected through the origin position detection circuit (15). It is connected to the reset terminal of the counter (13).

The offset position detection circuit (14) may be of any type as long as it can detect the peak P or P ′ at the center of the waveform shown in FIG. Although not limited to this, examples thereof are shown in FIGS. 3 and 4.

In the offset position detection circuit (14) illustrated in FIG. 3, the output of the offset magnetic detection element (11) is connected to a preamplifier (16), and the output of this preamplifier (16) is a peak detector (17). ) And is connected to one input terminal of an AND circuit (19) through a comparator (18), and the output of the peak detector (17) is input to the other input terminal of the AND circuit (19). It is connected. The threshold of the comparator (18) is set by the voltage divider resistor (20).

The operation of the offset position detection circuit (14) shown in FIG. 3 will be briefly described. The signal from the offset magnetic detection element (11) is amplified to a required level by the preamplifier (16). This signal is compared with the threshold value set by the voltage dividing resistor (20) and input to one terminal of the AND circuit (19), and the peak position is detected by the peak detector (17) and the AND circuit (17). 19) and the other terminal. Then, the AND circuit (19) outputs a detection pulse only when a peak higher than the threshold value set by the voltage dividing resistor (29) is input. By setting the threshold value of the voltage dividing resistor (20) higher than the peaks on both sides of FIG. 7 (a), the detection pulse is output at the central peak.

In the offset position detection circuit (14) illustrated in FIG. 4, the output of the offset magnetic detection element (11) is connected to the preamplifier (16), and the output of this preamplifier (16) is the peak detector (17). )It is connected to the. The output of the peak detector (17) is connected on the one hand to one input terminal of the AND circuit (19) and on the other hand to the flip-flop circuit (22) via the inverter (21).

The output of the flip-flop circuit (22) is connected to the other input terminal of the AND circuit (19), and the output of the AND circuit (19) outputs the delay circuit (24) and the OR circuit (23). It is connected to the reset terminal of the flip-flop circuit (22) through. An arbitrary input terminal for forced reset is further connected to the OR circuit (23).

The operation of the offset position detection circuit (14) shown in FIG. 4 will be briefly described. The signal from the offset magnetic detection element (11) is amplified to the required level by the preamplifier (16), and the peak detector (17) shows a low peak on one side and a peak in the center shown in FIG. 7 (a). P (or P ′) and the lower peak on the other side are detected in this order, and detection signals are output respectively. The output Q of the flip-flop circuit (22) is reset to high in the initial state.

The detection signal of the first peak (for example, the low peak on the left side) detected by the peak detector (17) is input to the flip-flop circuit (22), and the output Q is inverted to low. At this time, the peak detection signal from the peak detector (17) is input to the AND circuit (19), but since the output Q of the flip-flop circuit (22) is inverted to low, the output remains low. Is.

Next, the detection signal of the second peak (peak at the center) detected by the peak detector (17) is input to the flip-flop circuit (22), and the output Q is inverted to high. At this time, since the peak detection signal from the peak detection circuit (17) is input to the AND circuit (19) and the output Q 1 of the flip-flop circuit (22) is inverted to high, the peak detector (17) outputs the peak detection signal. During this peak detection signal, the output of the AND circuit (19) becomes high, which becomes the detection signal of the central peak shown in FIG. 7 (a).

When the detection signal indicating the central peak position is output from the AND circuit (19), the third peak (low peak on the right side) is passed through the delay circuit (24) and the OR circuit (23). The flip-flop circuit (22) is reset to the initial state after the delay time set after the detection.

The peak detector (17) used in the above offset position detection circuit (14) may be any one as long as it can detect an arbitrary peak of the input waveform and obtain a detection output. Although not limited thereto, examples thereof are shown in FIGS. 5 and 6.

The peak detector (17) illustrated in FIG. 5 integrates the input signal by the integrating circuit (27) and compares the integrated waveform by the comparator (28) with the input signal as a threshold. It is a thing. The peak detector (17) illustrated in FIG. 6 holds the maximum value of the input signal in the peak hold circuit (29) and compares the maximum value with the comparator (30) using the input signal as a threshold value. belongs to.

Next, the operation of the hydraulic cylinder with the position detector of the above embodiment will be described. The piston (2) advances by introducing the pressure of the hydraulic pump into the first chamber (25) from the first introduction port (5) and opening the second introduction port (6). 2) is determined by the flow rate of the hydraulic pump, the throttle valve (not shown), and the throttle amount (thickness) of the first inlet (5).

The piston (2) retracts by introducing the pressure of the hydraulic pump into the second chamber (26) from the second introduction port (6) and opening the first introduction port (5). The reverse speed of the piston (2) is determined in the same way as the forward speed. The introduction of hydraulic pressure into the first and second chambers (25) and (26) is performed by controlling a solenoid valve (not shown) by a signal from the CPU (12).

Before the length measurement is started, the offset magnetic detection element (11) is set at the position where the piston (2) passes the most by advancing and retreating, and in order to measure this position accurately, teaching according to the following procedure. I do.

First, as shown by the chain line in FIG. 1, the piston (2) is moved forward from the initial state in which the piston (2) is moved to the left end (origin). When the piston (2) starts to move forward, the origin magnetic detection element (7) outputs a signal as shown in FIG. 7 (a), and the origin position detection circuit (15) shows as shown in FIG. 7 (b). A pulse signal is output. At the rising edge of the pulse signal shown in FIG. 7B, the counter (13) is reset.

When the piston (2) moves forward, the roller (9) rolls on the surface of the rod (4) and a number of pulses proportional to the movement amount of the piston (2) is transmitted from the pulse encoder (8) to the counter (8). 13), the counter (13) outputs the detection pulse from the offset position detection circuit (14) by the offset magnetic detection element (11) detecting the magnetism of the magnet (3) after the reset. Count the number of offset pulses until

The offset pulse number is stored in the CPU (12). During this teaching, the piston (2) should not be reversed and retracted in the middle, and it is better to avoid stopping once. The best result is obtained by moving the piston (2) at a constant speed from the start to the end of teaching.

Next, the length measuring operation will be described. The counter (13) adds or subtracts the pulse from the pulse encoder (8) in accordance with the forward and backward movement of the piston (2) to keep the current position of the piston (2) at all times.

When the piston (2) reaches the position of the offset magnetic detection element (11) during the forward movement of the piston (2), this is detected and a detection pulse is output from the offset position detection circuit (14) to the CPU (12). ) Is output. In response to this detection pulse, the CPU (12) outputs an offset signal for correcting the counter (13) to the offset pulse number obtained by the teaching, and the counter (2) uses this offset signal for offsetting. It is corrected to an accurate number of pulses corresponding to the position of the magnetic detection element (11). This offset is performed every time the piston (2) passes through the position of the offset magnetic detection element (11) while advancing.

In the above embodiments, the counter (13) is offset when the piston (2) reaches the position of the offset magnetic detection element (11), but the present invention is not limited to this. Not a thing. For example, the value of the counter (13) when the piston (2) reaches the position of the offset magnetic detection element (11) is stored, and the stored counter is stored when the piston (2) is reversed next time. The difference between the value of (13) and the number of offset pulses may be added to or subtracted from the counter (2), and the error may be corrected before the next sampling of the data of the counter (13).

In the above embodiment, the accurate offset pulse number obtained by teaching is stored in the CPU (12), but the present invention is not limited to this, and the counter (13) is stored. It may be stored in another storage circuit or in another storage circuit.

In the above embodiments, the teaching is performed before the length measurement, but the teaching is not always necessary, and an arbitrary value is offset with the position of the magnetic detection element for offset (11) as a reference point. You may make it memorize | store as a pulse number.

In the above embodiment, the counter (13) is offset when the piston (2) passes through the position of the offset magnetic detection element (11) while advancing, but the present invention is not limited to this. The present invention is not limited to this, and may be performed when passing while moving backward, or may be performed when moving forward or backward.

In the above embodiments, the output signal processing circuit of the origin magnetic detection element (7) that outputs the same as the conventional output is used, but the present invention is not limited to this, and the offset magnetic detection element is used. As with the detection element (11), an element that detects the center of the peak of the detection signal may be used. By doing this, more accurate length measurement can be performed.

[0041]

[Effect of the device]

 As described above, according to the present invention, the magnetic detection element for offset is provided in the middle of the cylinder, and the error generated as the piston moves back and forth is corrected every time the position of the magnetic detection element is passed. The effect is that the counter value is always held at an accurate value and no error accumulates.

Further, since the counter value is offset to an accurate value in the middle of the cylinder, there is an effect that it is not necessary to return the piston to the home position each time the vehicle moves forward or backward. Furthermore, since the signal processing circuit of the magnetic detection element detects the peak apex and outputs the signal, there is an effect that the position of the detection output does not change due to temperature change.

[Brief description of drawings]

FIG. 1 is a sectional view of a cylinder of a length measuring machine according to the present invention.

FIG. 2 is a block diagram showing a position example of a control circuit of a length measuring device according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment of an offset position detection circuit.

FIG. 4 is a circuit diagram showing another embodiment of an offset position detection circuit.

FIG. 5 is a circuit diagram showing an embodiment of a peak detector.

FIG. 6 is a circuit diagram showing another embodiment of the peak detector.

FIG. 7A is a characteristic diagram showing an output of a magnetic detection element,
(B) is a characteristic diagram when the output of the magnetic detection element is pulsed with a half width.

FIG. 8 is a cross-sectional view showing a conventional length measuring device.

[Explanation of symbols]

(1) ... cylinder, (2) ... piston, (3) ... magnet,
(4) ... rod, (5) (6) ... differential oil inlet,
(7) ... Magnetic detection element for origin, (8) ... Rotary encoder, (9) ... Roller, (10) ... Spring, (11) ... Magnetic detection element for offset, (12) ... A / D converter,
(13) ... Counter, (14) ... Offset position detection circuit, (15) ... Origin position detection circuit, (16) ... Preamplifier, (17) ... Peak detector, (18) ... Comparator, (1
9) ... AND circuit, (20) ... Voltage dividing resistor, (21) ...
Inverter, (22) ... Flip-flop circuit, (23) ...
OR circuit, (24) ... Delay circuit, (25) ... First chamber, (26) ... Second chamber, (27) ... Integrating circuit, (28) ... Comparator, (29) ... Voltage dividing resistor, ( Three
0) ... comparator.

Claims (2)

[Scope of utility model registration request] 1. A piston connected to a rod is inserted into a cylinder so that the piston can advance and retreat, and an encoder that outputs a pulse as the rod advances and retracts is provided on the rod protruding side of the cylinder, and the pulse output of this encoder is counted by a counter. The offset detection element for detecting the piston is provided in the middle of the cylinder, and the value of the counter is corrected to the number of offset pulses each time the piston reaches the position of the offset detection element. Cylinder with position detector. 2. An offset position detection circuit for outputting a detection signal at the peak of the output of the offset detection element, a magnet built in the piston, an offset detection element composed of a magnetic detection element, and an offset position detection circuit. A cylinder with a position detector according to claim 1, wherein the value of the counter is corrected to the number of offset pulses based on the detection signal output of the position detection circuit.